Curable organopolysiloxane compositions that can be cured by a hydrosilylation reaction are used for forming protective coatings on photo-couplers, light-emitting diodes, solid-state imaging elements, or similar optical semiconductor elements among semiconductor devices. It is required that such protective coatings for semiconductor elements should neither absorb light generated or received by the aforementioned elements, nor should they dissipate this light.
A curable organopolysiloxane composition that is cured by a hydrosilylation reaction and that forms a cured body having a high refractive index and a high light transmissivity can be exemplified by the following: a curable organopolysiloxane composition comprising an organopolysiloxane having phenyl and alkenyl groups, an organohydrogencyclosiloxane, and a hydrosilylation-reaction catalyst (see Japanese Unexamined Patent Application Publication (hereinafter referred to as “Kokai”) H08-176447); a curable organopolysiloxane composition comprising a liquid or solid organopolysiloxane that contains phenyl and alkenyl groups and has viscosity at 25° C. equal to or greater than 10,000 mPa·s, an organohydrogenpolysiloxane having in one molecule at least two silicon-bonded hydrogen atoms, and a hydrosilylation catalyst (see Kokai H11-1619); and a curable organopolysiloxane composition comprising an organopolysiloxane having aryl and alkenyl groups, an organopolysiloxane having in one molecule at least two silicon-bonded hydrogen atoms, and a catalyst in the form of a platinum complex of an aryl-containing organosiloxane oligomer (see Kokai 2003-128992).
However, the aforementioned curable organopolysiloxane compositions are high in viscosity and therefore have poor fillability. Furthermore, they have poor curability since their curing reaction temperatures are high.
It is an object of the present invention to provide a curable organopolysiloxane composition that is characterized by good fillability and curability and that, when cured, forms a cured body that possesses a high refractive index, high light transmissivity, and strong adhesion to various substrates. It is another object to provide a semiconductor device that is made by using the aforementioned composition and that possesses excellent reliability.